Personal energy requirements This is how many calories your body needs
Whether you bite into an apple or eat a slice of bread, the body gets what it needs from food to live: protein, fats, carbohydrates. Apple, bread and other foods are crushed by the teeth and digested by the stomach. The food pulp then enters the small intestine: there, the food components are carried through the intestinal wall into the bloodstream. Proteins, fats and carbohydrates are too big to pass through, though. Only the smallest components get through. Therefore, enzymes in the small intestine break down proteins into amino acids and carbohydrates into simple sugar molecules. Fats are broken down into fatty acids and glycerol.
Amino acids, sugars, fatty acids and glycerol spread throughout the body via the bloodstream and lymphatic vessels. Your journey ends at the individual body cells. Once inside the cell, they enter its metabolism. Amino acids are often used as building materials, for example for the cell wall. Sugar molecules and fatty acids serve predominantly as energy sources. If there is too much of it, the excess ends up in fat storage – including sugar, as excess carbohydrates are converted into fat.
Energy is derived from sugar
The cell generates energy by burning sugar or fat with the help of oxygen. At the end of the transformation, carbon dioxide and water remain. Carbon dioxide is exhaled, the water is excreted.
With the help of energy, the body can regenerate, regulate body temperature, create new cells, tense muscles, dispose of defective cells, send nerve impulses through the brain – in other words, do everything it needs to live.
Because energy intake keeps people alive, they feel the need to eat. However, some people eat more than their body needs. Whether it is because the body sends out satiety signals too late, or because the food tastes so good – the consequence is the same: the person becomes too fat and susceptible to typical diseases such as high blood pressure or diabetes.
This is how much energy is in food
The most important source of energy for the body are carbohydrates. This includes sugar, but also starchy foods such as flour, pasta or potatoes. The body can also convert fats and even proteins into energy. Nutritionists use a calorimeter to determine how many calories each nutrient provides. This is a small kiln, which is loaded with the appropriate foods. As they burn, heat is released. This energy can be measured.
When fat burns, a lot of heat is generated. Carbohydrates and proteins cause less heat to be generated: So brings
- one gram of fat contains 39 kilojoules (about 9 kilocalories) of energy
- one gram of carbohydrates 18 kilojoules (about 4 kilocalories)
- one gram of protein 17 kilojoules (about 4 kilocalories)
This is how calories are converted into joules
Whether you measure heat in calories or joules is ultimately irrelevant, the amount of energy is the same. In Germany, the unit of measurement calories is the more common one, in most nutrition tables, joules are also recorded. If you want to convert one value to the other:
- 1 joule equals 0.2 calories
- 1 calorie is equal to 4.2 joules
The units kilocalorie and kilojoule denote respectively the thousandfold of the basic unit: one kilocalorie corresponds to one thousand calories, one kilojoule to one thousand joules. Incidentally, one calorie is quite a lot: it is the energy needed to heat one milliliter of water – that’s one thick drop – from 14.5 to 15.5 degrees Celsius.
Criticism of calorie counting
Critics of calorie counting point out that the body cannot be compared to a kiln in the laboratory. After all, the cells would metabolize the nutrients in complicated chemical processes, the ovens would just burn them up.
In the meantime, however, it has been clarified that the laboratory values of fat and carbohydrates actually correspond to the calorific values in the body. Only with the proteins this does not apply. When the organism breaks down proteins, urea is produced in addition to carbon dioxide and water. This substance contains additional energy – but it is excreted in the urine. The physiological calorific value of protein is therefore lower. In the above list the correct value is already given.
Your personal basic needs
How many calories a person consumes in a day in energy depends mainly on two factors: first, the basal metabolic rate – which is the energy the body needs to regulate essential things – and second, the physical activity of that person.
All organs and tissues are constantly consuming energy: the immune system, for example, is always fighting off invaders. Nerve impulses are constantly coursing through the brain, even during sleep, the heart never stands still, the lungs expand with each breath. Therefore, the body needs nutrients even at rest.
Women have a lower basal metabolic rate
The basal metabolic rate is determined above all by gender, age and muscle mass. The latter consumes more energy than fat tissue even at rest, so muscle mass is more important than pure weight. With increasing age, muscle mass is usually reduced, so there is more fat tissue, therefore the basal metabolic rate decreases with age. And since the percentage of fat in women is higher than in men, women also have a lower basal metabolic rate.
Basal metabolic rate is defined as energy expenditure at physical rest, after overnight fasting and at room temperature. Influences of the ambient temperature do not count. In concrete terms, this means that a man who rests and lies down in the morning with an empty stomach has a basal metabolic rate of about 4.2 kilojoules. The equivalent of one calorie – provided he has no fever and the bed is about room temperature. This calculated consumption is per kilogram of body weight per hour. A woman burns less under the same conditions: about 3.5 kilojoules.
This is how the basal metabolic rate is calculated
You can calculate your basic daily needs yourself. The formula is:
- body weight in kilograms
- multiplied by 24 hours
- multiplied by gender-typical consumption: women 3.5 kilojoules, men 4.2 kilojoules
A woman who weighs 60 kilograms, for example, needs at least 5040 kilojoules a day, which is about 1200 kilocalories. An 80-kilogram man burns 8064 kilojoules or about 1927 kilocalories at rest.
The body consumes less energy during sleep or in the case of hypothyroidism. The basal metabolic rate, on the other hand, increases immediately when
- strong emotions such as joy, anger, fear
As soon as a person becomes active, he needs additional energy – his calorie consumption increases. Like when he gets up and smears himself a sandwich. For example, he needs a particularly large amount of energy when he rides his bike to work quickly. The longer and heavier the activity, the more calories the body burns. This so-called power increase, together with the basic requirement, makes up the total energy requirement.
Women with consume a total of about 8400 kilojoules a day, which is about 2000 kilocalories; men burn more, about 10.500 kilojoules (about 2500 kilocalories). Those who work hard physically metabolize correspondingly more. Nutritionists estimate average daily turnovers like this:
- During light physical work, for example in the office, a person burns a total of between 8400 and 12.000 kilojoules (women from 2000 kilocalories, men up to 2800 kilocalories).
- In moderately hard physical work, for example as a car mechanic, there is an average of 16.000 kilojoules (about 3800 kilocalories);
- With physical heavy work, as for instance furniture packers do it, 20.000 kilojoules (about 4780 kilocalories) consumed.
Lose weight by exercising more
If you want to lose weight, you can either go on a diet or exercise more. Sport helps in any case, but you can also use every other possibility of movement to burn more energy: climb stairs more often instead of taking the elevator, do more on foot or ride a bicycle instead of driving a car. Even those who do household chores such as cleaning windows, mopping the floor or digging up the garden burn calories. However, the effect should not be overestimated. Something else is more decisive: these small activities help to lose less muscle mass when losing weight. This means that the energy metabolism does not drop as much.
Calorie consumption during sports
Those who exercise may eat more. Because when the body moves, it uses more energy. Therefore, sport is a good way to lose weight – provided that the person wanting to lose weight does not eat more than usual after training. Otherwise it quickly replaces the lost calories.
When jogging, the body burns about 42 kilojoules per minute, or about 10 kilocalories. Converted to one hour, this results in an energy consumption of 2520 kilojoules, or 600 kilocalories. Those who prefer to play soccer: Ten minutes consumes 378 kilojoules (90 kilocalories). A professional kicker burns up about 16.800 kilojoules (4.000 kilocalories). By comparison, professional cyclists competing in the Tour de France consume up to 42.000 kilojoules – that is about 10.000 kilocalories. Nutritionists have determined the energy consumption for almost any sport.